Incidental Histopathological Findings in Hearts of Control Beagle Dogs in Toxicity Studies

In preclinical studies of pharmaceutical agents, the beagle dog is a commonly used model for the detection of cardiotoxicity. Incidental findings, postmortem changes, and artifacts must be distinguished histopathologically from test item-related findings in the heart. In this retrospective analysis, cardiac sections from 88 control beagles (41 male, 47 female; ages 5-18 months) in preclinical studies were examined histopathologically. The most common finding was thickening of the tunica media of intramural coronary arteries, most likely a postmortem change. The second most common finding was the presence of vacuoles within Purkinje fibers. Dilated lymphatic and blood vessels at the insertion of chordae tendineae were noted more commonly in males than in females and were considered a normal anatomic feature. Mesothelial-lined papillary fronds along the epicardial surface of the atria were present in several dogs, as were small infiltrates of inflammatory cells usually within the myocardium. In summary, control beagles' hearts frequently have incidental findings that must be differentiated from test item-related pathologic changes. Historical control data can be useful for the interpretation of incidental and test item-related findings in the beagle heart.